1. Field of the Invention
The present invention relates to an optical transmission line suitably used for a large-capacity high-speed WDM optical transmission system, and an optical fiber and a dispersion compensating device suitably used for such an optical transmission line.
2. Related Background Art
An optical transmission system employing the WDM (Wavelength Division Multiplexing) scheme transmits a wavelength-multiplexed optical signal in the 1.55-μm wavelength band through an optical fiber transmission network and enables large-capacity high-speed communication. This optical transmission system is constructed by an optical fiber transmission line as an optical signal transmission medium, an optical amplifier for amplifying a wavelength-multiplexed optical signal at once, and the like. Various researches and developments have been made to enable larger-capacity higher-speed WDM communication.
For an optical transmission line, reduction of dispersion and a dispersion slope is an important subject of study. More specifically, when an optical transmission line has dispersion in the wavelength band of an optical signal, the waveform of optical signal sent from the transmitting station deforms through the optical transmission line to cause reception degradation at the receiving station, because the optical signal has a certain bandwidth though the signal is monochromatic. Hence, dispersion in optical transmission line is preferably as small as possible in the signal wavelength band. For large-capacity communication, dispersion in optical transmission line is desirably small in a signal wavelength band as wide as possible. Hence, the dispersion slope in the optical transmission line is also preferably as small as possible.